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Archives for the SPC Convective Outlook are updated daily (approximately) with a live map at the beginning of each article. Follow the link at the end of the article to check for current updates on the NOAA/NWS Storm Prediction Center website. Also, see Archives for Chicago's hourly weather data on CARDINAL NEWS Magazine.


Sunday, May 21, 2023

SPC May 21, 2023 0600 UTC Day 1 Convective Outlook

LIVE MAP (ABOVE) ... SPC 1200Z Day 1 Outlook Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1228 AM CDT Sun May 21 2023 Valid 211200Z - 221200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS THE INTERIOR NORTHWEST INTO WESTERN MONTANA... ...SUMMARY... Severe thunderstorms are possible across portions of the interior northwest into western Montana. Large hail and isolated damaging gusts will be possible with these storms. ...Eastern WA/OR to western MT... Upper high, currently centered over western NV, will weaken and sag south Sunday as a pronounced trough approaches the WA/OR Coast. Latest model guidance suggests 60-90m 12hr 500mb height falls will spread across WA/OR into the northern Rockies region late in the period. Leading edge of large-scale ascent should spread into the northern inter-mountain region by late afternoon as high-level diffluent flow aloft increases as far east as western MT. Pre-trough boundary-layer heating is expected to contribute to modest instability by mid afternoon as surface temperatures warm through the 70s at lower elevations. With cooling mid-level temperatures, lapse rates will steepen significantly and isolated-scattered thunderstorms should develop ahead of the surging cold front, initially across southeast BC into northeast WA by 21z, then farther south into eastern OR by 23z. Forecast soundings suggest ample surface-6km shear for organized rotating updrafts, and isolated supercells are probable, along with a mixed mode of multi-cells and a few clusters. Large hail is expected with the strongest updrafts and gusty winds may also accompany some of this activity. Convection should spread east-northeast toward western MT, by late evening, in advance of the progressive mid-level trough. ..Darrow/Thornton.. 05/21/2023 Read more CHECK UPDATE ZOOM GRAPHIC
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